Camera-projector with vacuum film platen

ABSTRACT

Camera-projector having a frame-enclosed transparent platen supported on the first surface of its condenser, the peripheral edge of the platen being spaced from the frame to provide a continuous channel thereabout which is connected to an evacuating pump. The frame has registration pins by which film is located on the platen with its margin over the channel, and the edge of the platen is notched at spaced intervals to promote vacuum pull down of the film flat against the platen surface.

United States Patent Wally, Jr.

[54] CAMERA-PROJECTOR WITH VACUUM FILM PLATEN [72] lnventor: Joseph H.Wally, Jr., Shawnee Mission,

Kans.

[73] Assignee: Western Blue Print Co., Kansas City, Mo. [22] Filed: May27, 1970 [21] Appl. No.: 40,881

[52] US. Cl ..355/76, 355/73, 353/23, 353/95 [51] Int. Cl. ..G03b 27/64[58] Field ofSearch ..355/73,76;353/23,95, 120, 353/ 122 [56] ReferencesCited UNITED STATES PATENTS 3,433,564 3/1969 Lahr ..355/76 Feb. 29, 19723,115,808 l2/l963 Durst ..355/73 Primary ExaminerSamuel S. MatthewsAssistant Examiner-E. M. Bero Attorney--.lohnson, Dienner, Emrich,Verbeck and Wagner [57] ABSTRACT Cameraprojector having a frame-enclosedtransparent platen supported on the first surface of its condenser, theperipheral edge of the platen being spaced from the frame to provide acontinuous channel thereabout which is connected to an evacuating pump.The frame has registration pins by which film is located on the platenwith its margin over the channel, and the edge of the platen is notchedat spaced intervals to promote vacuum pull down of the film flat againstthe platen surface.

18 Claims, 8 Drawing Figures 1 CAMERA-PROJECTOR WITH VACUUM FILM PLATENThis invention relates generally to photographic apparatus andparticularly to apparatus which is used to photograph an image ofgraphic sheet material on film and thereafter to projection-print copiesthereof using the negative processed from the film. However, as will beapparent, the invention is not restricted to such apparatus and willhave utility in other apparatus.

The principal object of the invention is to provide novel and improvedmeans in such apparatus for supporting film and/or a negative processedtherefrom.

In my application for US. Pat, Ser. No. 836,317, filed June 25, 1969,there is disclosed a camera-projector having an optical head whichcontains an objective and is provided with a platen spaced behind theobjective on which the film is located when using the apparatus tophotograph material mounted on a vertical subject holder in front of theoptical head. The optical head moves along overhead tracks toward andaway from the subject holder in accordance with the image reductionfactor required. The objective is also independently adjustable withinthe optical head toward and away from the film platen to permitsharpening image focus for different spatial settings of the opticalhead, more particularly its film platen, from the subject holder.

The platen is transparent and the optical head includes a point sourceof light and condenser lens means which are positioned'behind the filmplaten and utilized to project an image of the negative on the filmplaten to sensitive paper mounted on the subject holder in order toprint a copy or copies thereof. The same or different spatial settingsfor the optical head and its objective may be used in accordance withimage magnification or reduction requirements for the copy.

Because of the rigidity and precise arrangement of the structure makingup the apparatus, the apparatus is not subject to vibration and axialadjustments of the relative spacings of the objective and the subjectholder relative to the film platen may be made without altering theirprecise angular disposition and alignment to the optical axis of theapparatus. These features, plus the fact that the same objective isutilized both in the original projection of the subject to the film andin the subsequent projection of the film image to the subject holdermakes it possible to obtain excellent reproductions or copies of theoriginal. Moreover, by following techniques such as described in mymentioned patent application, Ser. No. 836,317, it is also possible todifferently expose several films of the same subject or to make severalcopies of one film image, the copies or film images being taken underdifferent conditions of objective focusing and illumination of thesubject and thereafter to combine them into a composite which will havea clarity, line delineation and uniform line intensity considerablyimproved over the original.

Success of such a project as well as copy work generally depends on anability to hold the films and/or the negatives processed therefrom bothin the same axial aligned or registered relation to the optical axis ofthe apparatus, but most importantly in the same reference plane. Thedeveloped film emulsion must be located in exactly the same referenceplane when itis projected back to the subject holder as it was whenfirst exposed. To the extent that the film emulsion is distorted as bylocating a cover glass thereover or wrinkling of the film the compositeor copy will suffer.

in my mentioned application for patent, Ser. No. 836,317, I describegrinding the film-supporting surface of the transparent platen to asflat a plane as practicable which I accurately and precisely angle tothe optical axis of the lens or platen. I also describe arranging aframe spaced about the peripheral edge of the platen in order to leave acontinuous narrow channel thereabout to which an air-evacuating pump isconnected. Also, along the upper side of the frame I describe locatingregistration pins by means of which prepunched film and negativesprocessed therefrom may be located on the platen surface in the sameaxial relation to the objective; because the film is so dimensioned thatits margin overlies the surrounding channel the image area of the filmsand negatives can be tightly drawn against the platen surface and in thesame registered relation.

I, however, have found that variables such as film thickness, rigidityor flexibility and other physical characteristics which vary betweenindividual films as well as between a film and the negative processedtherefrom, the film or negative does not every time exactly conform tothe surface shape of the platen. This is because of the tendency of thefilm margin immediately adjacent the channel to seal with the inner edgeof the channel before the air is fully withdrawn from between the platensurface and the overlying film. Furthermore, the air entrapped betweenthe film and platen surface may vary in amount and also in location overthe image area. The images formed in the emulsion are not always locatedin the same reference plane and the variation therefrom is random andcannot be predicted.

it is therefore a principal object of this invention to providephotographic apparatus, for example the camera-projector abovedescribed, with means which will facilitate more accurately andprecisely drawing the film or negatives to the supporting surface of theplaten than previously possible.

In accordance with this object, this invention provides means whichdelay or inhibit seal of the outer margin of the film or negativeadjacent the evacuation channel until the air more centrally of theplaten surface beneath the film has been withdrawn.

Thus, it is a feature of the invention that the inner edge of thechannel or periphal edge of the platen is notched, grooved or otherwiseprovided with openings which establish communication between the airevacuation channel and an area of the platen surface beyond the shoulderof the inner wall of the channel where the film tends to first sea] asit is drawn into the mouth of the channel mouth during the evacuation ofair therefrom.

A further feature of the invention is that means outside the image areaof the film are provided to resist or delay the drawing of the overlyingfilm margin into the channel. One way I so this is by locating theshoulder of the outer wall of the channel about the platen at a heightsuch that it defines a plane which is higher than the plane defined bythe shoulder of the inner wall of the channel. A second way I do this isby providing restricting means which bridge the channel at spacedintervals about the platen.

A further feature of the invention is the novel means which I employ forsupporting the platen within its encircling frame.

In accordance with the invention, the edge of the platen whichconstitutes the shoulder of the inner wall of the channel is slightlybeveled and retaining clips are employed to bridge the channel at spacedintervals and engage said beveled edge. These clips have their outerends fastened in provided recesses off the frame and the underside oftheir inner ends being complementarily inclined to engage the bevelededge of the platen to retain the platen in secured position. The outerplanar surfaces of the clips, however, are substantially flush with thesurface of the platen so as to avoid any warping of the film at theplaten edges; and the width, spacing, as well as number of said clipsserve not only to securely hold the platen in place but also provideresistance to the film margins being drawn into the channels.Preferably, the upper surface of the clips are grooved across thechannel bridging area thereof to further facilitate conformity of thefilm in that area to the pull of the air-evacuating pump.

Ancillary to the above-described role which the beveled edges of theplaten play with the retaining clips, the beveled shoulder may alsosoften any remaining tendency of the film to warp as it is pulled intothe channel under the force of the evacuating pump.

Thus it is an important feature and/or advantage of the invention thatmeans are provided whereby films and/or negatives processed therefromcan be drawn tightly into conformity with the surface of the platenwithout wrinkling and entrapment of air therebeneath. Of consequence,the image area of both the film and the processed negative can berepetitively I provided for mounting the platen to the first surface ofthe condenser. Because the platen is separate from the condenser and isnot fused or otherwise cemented thereto, its opposed surfaces, andparticularly it film receiving surface, can be formed while the platenis separated from the lens holder. Thereafter the platen with its groundsurfaces can be conveniently assembled in the frame and secured by theretaining clips in a proper axial aligned position relative to thecondenser without disturbing or injuring the ground planar parallelsurfaces thereof.

-Many other objects, advantages and/or features of the invention will beapparent from the more specific description of a preferred embodiment ofthe invention which will now be described in connection with the severalfigures constituted by the accompanying drawings.

In said drawings:

FIG. 1 is a side elevational view of a photographic apparatus with whichthe invention is utilized;

FIG. 2 is a view taken along lines 22 in FIG. 1 looking in the directionindicated by the arrows and is a plan view of the film platen andillustrates its manner of mounting on the condenser lens supportingstructure;

FIG. 3 is a sectional view taken along lines 33 in FIG. 2 looking in thedirection indicated by the arrows and shows further details of themanner of mounting film platen to the condenser lens supportingstructure;

FIG. 4 is a sectional view taken along lines 4-4 of FIG. 2 looking inthe direction indicated by the arrows and illustrates on an enlargedscale the manner in which the retaining clips are utilized to secure thefilm platen;

FIG. 5 is a fragmented plan view of the retaining clips as illustratedby FIG. 4; a

FIG. 6 is a sectional view taken along lines 6-6 of FIG. 2 looking inthe direction indicated by the arrows and shows details of the platenand the registration pins utilized therewith to locate film on theplaten;

FIG. 7 is a sectional view taken along lines 77 of FIG. 2 andillustrates the inclined notches in the periphery of the platen on aconsiderably enlarged scale; and

FIG. 8 is a fragmented plan view of the portion of the platenillustrated in FIG. 7.

Referring now more particularly to the several views wherein like partsare identified by like reference numerals, FIG. 1 illustrates acamera-projector with which the present invention is useful. Such anapparatus is disclosed and claimed in my mentioned copending applicationfor US. Pat., Ser. No. 836,317, to which reference may be had for afuller understanding of its construction and operation. However, forpurposes of understanding this invention, it will suffice to point outthat the apparatus illustrated by FIG. 1 comprises an optical headindicated generally at 12. Said optical head is suspended by front andrear pairs of wheels 14 which move along a pair of tracks 16 mounted onopposed sides of an overhead rigid supporting structure 18 shownsupported at one end by columnar structure 20 and at its forward end bystructure comprising a subject holder 22 relative to which the opticalhead moves. The optical head 12 comprises a pair of planoconvexcondenser lenses 24, 26 arranged with their convex surfaces facing, asis conventional. Said condenser lenses are enclosed within a dusttightboxlike enclosure or supporting structure 28 having an axially alignedlight aperture in the front and rear walls thereof. As will afterwardsbe explained more in detail, the forward wall of structure 28 comprisesa jig plate 50 having a light aperture 62 of generally rectangular shapeover which is supported the film platen 72 comprising the presentinvention. Access to said platen 72 for locating the film or negativethereon is obtained through door 30 in plenum 54. At 32 is an objectivesupported by lens board 34 and at 36 is a point source of lightsupported by light board 38. Lens board 34 and light board 38 aremounted on massive sized rigid precisely related tubular ways 40 whichaccommodate axial adjustment of the spatial relation of the objectiveand point source of light relative to the film platen 72.

Subject holder 22, as more particularly illustrated and described in mymentioned copending application, comprises a vertically disposedtranslucent member 42 having a planar subject-receiving surface facingthe optical head 12 and surrounded by a peripherally located continuouschannel connected to an air evacuating pump, not shown. At 44 is astructure supporting fluorescent bulbs or other illuminating means bywhich the translucent member 42 may be back-lighted. At 46 is a roll ofpliofilm or other suitable flexible transparent plastic sheet secured atthe top of the subject holder and dimensioned to overlie the mentionedair-evacuating channel about the periphery of the translucent member 42when unrolled. Sheet material to be copied or sensitive paper on whichan image of the copy is to be printed is located within the area of thetranslucent member 42 defined by the air-evacuating channel and thepliofilm roll 46 unrolled thereacross so as to be drawn tightly againstthe surface of the subject holder 42 with evacuation of air from thementioned channel. The unrolled pliofilm sheet thus tightly holds thesheet material or sensitive paper against the flat vertical surface ofthe translucent member 42 during the photographing or projectionprinting operation.

Optical head 12 as thus described may be utilized as a camera with itspoint source of light 36 deenergized or as a projector when the lightsource is illuminated. The optical head is moved toward or away from thesubject holder to locate its film platen 72 at the proper spatialsetting or distance from the surface of the subject holder 22 tointroduce a desired image reduction factor when the apparatus is used asa camera or to induce a magnification factor when it is used as inprojection printing. The objective 32 is independently adjustable onways 40 toward and away from the film platen 72 by moving lens board 34and this adjustment serves to sharpen the focus of the projected image.

Referring therefore now to FIGS. 2 through 8, and first to FIGS. 2 and3, the novel construction of film platen and supporting structuretherefor comprising the present invention will be described. As shownbest by FIG. 3, the condenser lens housing28 includes a front jig plate50 to which the flanged end of the condenser lens housing sidewalls aresecured as by screws 52. Jig plate 50 also serves as means to which thefilm plenum or housing 54 is secured, as by screws 56. The rear or innerside of jig plate 50 is suitably recessed to provide a circular seatwhich receives the flat surface 58 of the front condenser lens 24. Saidcondenser lens 24 is removably secured to the jig plate as by clips 60.Rubber or other suitable cushioning material may be located between theclips 60 and the convex surface of the condenser lens which they engage.Light aperture 62 in the jig plate 50 is of generally rectangular shapeand will have dimensions corresponding to the most useful, opticallyspeaking, area of the condenser lens. The inner peripheral wall of thejig plate defining said light aperture 62 is suitably recessed, as shownin FIG. 4, to define a lip 64 providing a continuous surface 68 on whichthe outer margin of the transparent platen 72 seats and an upstandingwall 70 which is disposed essentially normal, i.e., at right angles, tosurface 68. Surface 68 of the lip 64 is carefully machined so that itdefines a plane paralleling the plane of the flat surface 58 of thefront condenser lens 24 which is assembled with the jig plate on itsrear side. Said surface 68 is therefore disposed at right angles to theoptical axis of both the objective and the condenser lenses, as well asto the direction in which the optical head and objective move alongtrack 16 and ways 40. Transparent platen 72 is generally rectangular inshape and has a length and width slightly larger than the correspondingdimensions of aperture 62 so that it may stably seat on lip 64. Itslength and width, however, are less than the separation of the opposedstanding walls 70 about the lip so as to form a continuous channel 100about the periphery of the platen. Preferably, surface 68 of the lip iscovered by a thin strip of tape 80 adhesively coated on both surfaces.Said tape aids in locating the platen on the lip during assembly. Italso cushions and seals the outer margin of the platen to said-lipsurface 68. Prior to its assembly, the outer or film receiving surface76 and inner wall 86 is substantially flush with the inner wall 70 ofthe jig.

plate and together therewith forms the outer wall of the channel 100.The thickness selected for framing plate 84 is such' that its upper flatsurface defines a plane slightly higher or beyond the plane defined bythe outer surface 76 of the platen 72. In the flat upper surface 89 ofsaid frame plate 84 are recesses 90 suitably spaced about the peripheryof the channel 100 or platen 72. In said recesses 90 are fastenedretaining clips 92 as by screws 94. Said clips 92 have portions whichbridge across the channel and terminate in beveled ends which overlyingengage the peripheral shoulder 88 of the platen which is complementarilybeveled. The depth of said beveled shoulder 88 and the thickness of theclips 92 are so related that the outer surface of the clips aresubstantially flush with the outer surface 76 of the platen. Openings 96in the retaining clips through which fastening screws 94' extend arepreferably elongated in the direction of the platen edge to accommodatetheir axial adjustment to appropriately secure the platen in positioncentered over the light apertures 62 with continuous channel 100 aboutthe periphery thereof. The fastening screws 94 are then tightened andthe elongated openings filledwith a suitable mastic material.

Considering now FIG. 6 with FIG. 2, along the upper edge of the platento the outside of channel 100, registration pins indicated generally at98 are press fitted into provided openings in the framing plate 80. Asshown in FIG. 2, the pins 98 comprise three in number although any otherconvenient number of pins may be utilized. Under some circumstances, aswhen working with larger sized films, registration pins 98 may also beprovided in frame 80 along the bottom edge of the platen,or along allfour sides thereof. As illustrated by FIG. 6, each said registrationpins includes an inner cylindrical portion 98a and an outer or entrantmore spherical or tapered portion 98b. The cylindrical portion 98a ofsaid registration pins has a height of approximately 0.035 inches or atleast the thickness of the film of which the apparatus is utilized. Thediameter of the cylindrical portion 98b is the same as or slightlylarger than the diameter of the circular openings which are punched inthe film F, so that the film snugly fits and is not loose about thepins; and the entrant end 98b of the pins progressively decreases indiameter therefrom to its outer end for easier impalement and removal ofthe films. The registration pins thus serve to exactly register eachfilm, including those in which the punched holes may be slightly out ofline, each time in the same axial relation to the objective point oflight source and other structure of the apparatus.

Channel 100, as shown in FIG. 2 is connected by suitable conduits to anair evacuating pump (not shown). Said conduits comprise a pair ofopenings 102 which are drilled through the jig plate 50 from spacedlocations in their upper edge of the jig plate 50 from terminate insections 104 of smaller diameter disposed immediately below the channel100, asillustrated by FIG. 4. The reduced diameter of said openings 104is selected to avoid breaking into the wall of the lip 64. Openings 102provide connection to piping illustrated at 106 leading to the airevacuating pump and the inner ends of said openings of reduced diameter104 establish communication with the channel 100 by milled section 108in the base of said channel. Thus, as illustrated by FIG. 4, as well asFIG.

2, the dimensions of film F are selected so that its marginal portionsoverlie channel on all four sides of the transparent platen whenproperly assembled with its prepunched openings over registration pins98. Evacuation of air from the channel 100 under the pull of thementioned pump will therefore withdraw the air from between the film Fand the film supporting surface 76 of the platen 72 to cause the film Fto conform to the flat shape of the platen surface 76. In the large filmsizes with which the present invention is concerned (in the order of 8Xl 0 inches) I have noted that there is a tendency for thefilm to seal atthe outer shoulder of the platen constituting the inner wall and channelbefore all of the air has been withdrawn into the channel from beneaththe more central or image area of the film. This results in wrinkles anddistortion in the image area. One way to compensate therefor is for theoperator to quickly wipe across the film. However, unless particularcare is exercised in the wiping action there is the possibility ofinjuring the emulsion layer. I have found that by increasing the heightof the framing plate such that shoulder 114 of the outer wall of thechannel 100 lies in a plane above the plane of the outer or filmreceiving surface 76 of the platen, as illustrated at a in FIG. 6, theslight upward deflection of the film over the channel tends tomomentarily delay the pull of the film into the mouth of the channel 100under the force of the air evacuating pump. This pull of the film intothe channel 100 is also resisted by the portions of the retaining clipswhich span the channel 100.

However, it is a feature of this invention that I also notch theperipheral edge of the film platen 72 at selected intervals between theclips 92 and at a sufficient inclination that the channel hascommunication with the film-receiving surface 76 of the platen inwardlyof its outer shoulder 88 and therefore beyond the point at which thefilm tends to initially seal in response to evacuation of air fromchannel 100. As illustrated by FIG. 6, these slots should be inclined atan angle steep enough to establish their communication with the channel100 not only below the bevel, but below the expected depth to which thefilm may be drawn into the channel under the pull of the air evacuationpump and it also should extend far enough inwardly of the outer edge ofthe surface 74 of the platen to be beyond the point of initial seal. Ihave found that a useful angle of inclination will be in the order of 30to 40 to the platen surface 76. Preferably the opening of the slot 120into the platen surface 76 will lie wholly outside the periphery of thelight aperture 62 as defined by lip 64 at AA (FIG. 6) so that anywarping at its opening into the platen surface 76 will fall outside theimage area of the film. However, the width of these slots can be sominute that, in fact, they will introduce essentially no noticeabledistortion or warping of the film. For example, in a typicalconstruction wherein the transparent platen has a dimension ofapproximately 8Xl0 inches slots 120 may have a width of only a fewthousandths of an inch. Advantageously, however, they should be uniformin size and more or less equally spaced about the periphery of theplaten. To assume maximum hold down of the film a portion of the clips90 which bridge the channel should also be grooved the full width of theclip as at 122 and the groove width should approach the width of thechannel 100. The illustrated vee-shape permits a maximum width ofgroove.

It will thus be apparent that each film can be accurately aligned on thefilm platen surface 76 by means of the registration pins 98 and inresponse to the air evacuation pump will be caused to tightly conform tothe platen surface 76 with essentially no air entrapment therebetween.Of consequence, the emulsion layer of the film will always be located inthe same reference plane, as well as in the same angular and axialdisposition to the objective and subject holder.

Thus it will be apparent from the aforedescription that all of therecited objects, advantages and features of the invention have beendemonstrated as obtainable and in a highly practical convenient manner.Furthermore, it will be understood that the aforesaid description is notto be taken in a limiting sense, but as exemplary of one form of theinvention, the

scope and limits of the invention being defined by the claims heretoappended.

Thus having described my invention, l claim: 1. In an image-projectingsystem including a condenser lens and an objective lens spaced forwardlythereof, means on the side of the condenser lens facing the objectivewhich define a film supporting surface axially aligned with thecondenser lens and objective lens, said surface having a peripheraledge, and a continuous air-evacuating channel about said peripheral edgeof said film supporting surface, film registration means along at leastone side of said film-supporting surface for locating a film on saidsupporting surface with its margins overlying said I air-evacuatingchannel, said air-evacuating channel having an inner wall at theperipheral edge of the film supporting surface, an outer wall oppositesaid inner wall and a basewall therebetween, and spaced openings in theinner wall of said air evacuating channel which communicate at one endwith the channel and at their other end with the film sup portingsurface at a locus inwardly of its peripheral edge.

2. The combination of claim 1 wherein the outer wall of said channel iswider than the inner wall to define a shoulder forward of the filmsupporting surface.

3. The combination of claim 1 wherein the film supporting surface isflat, the inner wall of the channel is at right angles thereto, and theopenings comprise slots disposed at an angle intermediate thedisposition of said inner channel wall and film supporting surface.

4. The combination of claim 1 wherein the film-supporting surface isrectangular in shape and the openings comprise narrow slots disposed inthe edge of the film supporting surface at an acute angle with respectto the film-supporting surface.

5. The combination of transparent, solid means defining afilm-supporting surface axially aligned with the lens means of animage-projecting device and surrounded by a continuous air-evacuatingchannel, said channel having an inner wall with an upper shoulderadjacent the film-supporting surface and an outer wall with an uppershoulder opposite said inner wall, film holding means for locating afilm on said surface with its image area centrally of said surface andits margins overlying said channel, conduit means connecting saidchannel to an air evacuator operable to withdraw air from said channel,and further means outside said central area of the film supportingsurface which underlies the image area of the film, said further meanspreventing seal of the film margins with the shoulder of the inner wallof the channel before the film margin seals with the shoulder of theouter wall of the channel as said film margins are drawn into thechannel in response to evacuation of air therefrom so as to increase theevacuation of air and reduce entrapment of air between the image area ofthe film and the supporting surface as the film margins are drawn to thechannel whereby the image area of the film will closely conform to thefilm supporting surface.

6. The combination of claim 5 wherein said further means includes theupper shoulder of the outer wall of the channel which is higher than theupper shoulder of the inner wall of the channel and the film supportingsurface.

7. The combination of claim 5 wherein said further means includesinclined slots in the inner wall of the channel adjacent thefilm-supporting surface which communicate with the channel and the filmsupporting surface at a locus spaced inwardly of said channel.

8. In combination, a condenser lens holder which includes a lightaperture containing member to overlie one side of the condenser lens, atransparent platen supported on said member over said aperture andhaving a film-supporting surface, means defining a continuous channelabout the film-supporting surface of said platen which connects to anair evacuator, spaced film registration pins along an edge of saidsurface which locate a film on said surface with its margin overlyingthe channel, and said channel having an inner wall adjacent the filmsupporting surface with indentations at spaced intervals whichcommunicate with the channel and the film supportirliglsurface,

9. e combination of claim 8 wherein the inner wall of the continuouschannel has a shoulder in the plane of the film-supporting surface andthe channel has an outer wall spaced from the inner wall and more remotefrom the film-supporting surface, said outer wall of the channel havinga shoulder comprising a plane above said plane of the film-supportingsurface.

10. The combination of claim 8 wherein the shoulder of the inner wall ofthe channel is beveled.

11. The combination of claim 10 wherein the indentations comprise slotswhich are inclined and of a length so as to establish communication withthe channel below said beveled shoulder and with the film supportingsurface of the platen inwardly of said beveled shoulder.

12. The combination of claim 11 further including spaced bridgingelements which extend across the channel and engage the beveled shoulderof the inner wall of the channel.

13. In combination, a condenser lens and a condenser lens holderincluding a light-aperture-containing frame member which overlies oneside of the condenser lens, said frame member having an upper surfaceand a continuous lip about the periphery of said aperture which isdisposed below the upper surface of said member and an upwardlyextending wall surface between said lip and said upper surface, atransparent platen having an upper film receiving surface and mountedwith its lower peripheral edge seated on said lip and spaced from saidupwardly extending surface to define a continuous channel peripherallydisposed about the film-receiving surface of the platen, conduit meanscommunicating with said channel for connection to an air evacuator,retaining clips engaging the periphery of said platen and fastened tosaid member so as to secure the platen thereto, and the upper peripheraledge of said platen being notched at spaced intervals providingcommunication of the channel with marginal portions of the platensurface inwardly of the channel when a film is located on the platenwith its margin overlying said channel to facilitate drawing the filminto close conformity with the platen surface with evacuation of airfrom the channel.

14. The combination of claim 13 wherein the upper peripheral edge of theplaten is beveled and the retaining clips have one end engaging saidbeveled upper peripheral edge of the platen, the clips being securedwithin a provided recess in the frame member, and the upper surface ofthe clip being essentially flush with the upper platen surface.

15. The combination of claim 14 wherein the portion of the clip bridgingthe channel includes a groove on its upper side.

16. The combination of claim 14 wherein the surface of the platen is ina plane below that of the frame member.

17. The combination of claim 13 wherein the frame member includes filmregistration means along at least one side edge of the platen with whichfilm is registered in mounting on the film receiving surface of theplaten.

18. The combination of claim 17 wherein the upper platen surface isvertically disposed and comprises a rectangularshaped flat surface.

1. In an image-projecting system including a condenser lens and anobjective lens spaced forwardly thereof, means on the side of thecondenser lens facing the objective which define a film supportingsurface axially aligned with the condenser lens and objective lens, saidsurface having a peripheral edge, and a continuous air-evacuatingchannel about said peripheral edge of said film supporting surface, filmregistration means along at least one side of said film-supportingsurface for locating a film on said supporting surface with its marginsoverlying said air-evacuating channel, said air-evacuating channelhaving an inner wall at the peripheral edge of the film supportingsurface, an outer wall opposite said inner wall and a base walltherebetween, and spaced openings in the inner wall of said airevacuating channel which communicate at one end with the channel and attheir other end with the film supporting surface at a locus inwardly ofits peripheral edge.
 2. The combination of claim 1 wherein the outerwall of said channel is wider than the inner wall to define a shoulderforward of the film supporting surface.
 3. The combination of claim 1wherein the film supporting surface is flat, the inner wall of thechannel is at right angles thereto, and the openings comprise slotsdisposed at an angle intermediate the disposition of said inner channelwall and film supporting surface.
 4. The combination of claim 1 whereinthe film-supporting surface is rectangular in shape and the openingscomprise narrow slots disposed in the edge of the film supportingsurface at an acute angle with respect to the film-supporting surface.5. The combination of transparent, solid means defining afilm-supporting surface axially aligned with the lens means of animage-projecting device and surrounded by a continuous air-evacuatingchannel, said channel having an inner wall with an upper shoulderadjacent the film-supporting surface and an outer wall with an uppershoulder opposite said inner wall, film holding means for locating afilm on said surface with its image area centrally of said surface andits margins overlying said channel, conduit means connecting saidchannel to an air evacuator operable to withdraw air from said channel,and further means outside said central area of the film supportingsurface which underlies the image area of the film, said further meanspreventing seal of the film margins with the shoulder of the inner wallof the channel before the film margin seals with the shoulder of theouter wall of the channel as said film margins are drawn into thechannel in response to evacuation of air therefrom so as to increase theevacuation of air and reduce entrapment of air between the image area ofthe film and the supporting surface as the film margins are drawn to thechannel whereby the image area of the film will closely conform to thefilm supporting surface.
 6. The combination of claim 5 wherein saidfurther means includes the upper shoulder of the outer wall of thechannel which is higher than the upper shoulder of the inner wall of thechannel and the film supporting surface.
 7. The combination of claim 5wherein said further means includes inclined slots in the inner wall ofthe channel adjacent the film-supporting surface which communicate withthe channel and the film supporting surface at a locus spaced inwardlyof said channel.
 8. In combination, a condenser lens holder whichincludes a light aperture containing member to overlie one side of thecondenser lens, a transparent platen supported on said member over saidaperture and having a film-supporting surface, means defining acontinuous channel about the film-supporting surface of said platenwhich connects to an air evacuator, spaced film registration pins alongan edge of said surface which locate a film on said surface with itsmargin overlying the channel, and said channel having an inner walladjacent the film supporting surface with indentations at spacedintervals which communicate with the channel and the film supportingsurface.
 9. The combination of claim 8 wherein the inner wall of thecontinuous channel has a shoulder in the plane of the film-supportingsurface and the channel has an outer wall spaced from the inner wall andmore remote from the film-supporting surface, said outer wall of thechannel having a shoulder comprising a plane above said plane of thefilm-supporting surface.
 10. The combination of claim 8 wherein theshoulder of the inner wall of the channel is beveled.
 11. Thecombination of claim 10 wherein the indentations comprise slots whichare inclined and of a length so as to establish communication with thechannel below said beveled shoulder and with the film supporting surfaceof the platen inwardly of said beveled shoulder.
 12. The combination ofcLaim 11 further including spaced bridging elements which extend acrossthe channel and engage the beveled shoulder of the inner wall of thechannel.
 13. In combination, a condenser lens and a condenser lensholder including a light-aperture-containing frame member which overliesone side of the condenser lens, said frame member having an uppersurface and a continuous lip about the periphery of said aperture whichis disposed below the upper surface of said member and an upwardlyextending wall surface between said lip and said upper surface, atransparent platen having an upper film receiving surface and mountedwith its lower peripheral edge seated on said lip and spaced from saidupwardly extending surface to define a continuous channel peripherallydisposed about the film-receiving surface of the platen, conduit meanscommunicating with said channel for connection to an air evacuator,retaining clips engaging the periphery of said platen and fastened tosaid member so as to secure the platen thereto, and the upper peripheraledge of said platen being notched at spaced intervals providingcommunication of the channel with marginal portions of the platensurface inwardly of the channel when a film is located on the platenwith its margin overlying said channel to facilitate drawing the filminto close conformity with the platen surface with evacuation of airfrom the channel.
 14. The combination of claim 13 wherein the upperperipheral edge of the platen is beveled and the retaining clips haveone end engaging said beveled upper peripheral edge of the platen, theclips being secured within a provided recess in the frame member, andthe upper surface of the clip being essentially flush with the upperplaten surface.
 15. The combination of claim 14 wherein the portion ofthe clip bridging the channel includes a groove on its upper side. 16.The combination of claim 14 wherein the surface of the platen is in aplane below that of the frame member.
 17. The combination of claim 13wherein the frame member includes film registration means along at leastone side edge of the platen with which film is registered in mounting onthe film receiving surface of the platen.
 18. The combination of claim17 wherein the upper platen surface is vertically disposed and comprisesa rectangular-shaped flat surface.